In geotechnical engineering, one factor, among others, for consideration when designing geotechnical systems is the particulate-continuum interface. This interface occurs between the soil and the geotechnical structural members (e.g. soil-concrete, soil-steel, and soil-geomembrane). Although a significant amount of research has been performed on the behavior of soil masses under typical loading and straining conditions in geotechnical systems, the region where the geotechnical structural members and soil masses come into contact—the soil-geomaterial interface—has received markedly less attention.
The interface is a factor, among others, governing the performance of many geotechnical systems, including for example deep foundations, micro-tunneling, liner systems (e.g. landfills, canal liners, and leach ponds), and an assortment of retaining structures such as anchored, reinforced, and soil nailed walls. The importance of the characteristics and behavior of the interface between man-made geomaterials and soils in the overall system performance varies from application to application, but is usually reflected in some manner in the design methodology and associated calculations for each geotechnical system. Because the structural integrity of many systems is dependant upon accurate calculations and designs for the soil-geomaterial interface, correctly measuring the performance characteristics of the interface is crucial.
Another factor for consideration when designing geotechnical systems is the pressure of the fluid phase of permeable soils and sediment, which is called the pore fluid pressure. The measurement of pore fluid pressure can facilitate the identification of the groundwater table elevation, as well as the strength, compressibility, and permeability of the soil.
There are many different types of penetrating probes for detecting and measuring soil properties and characteristics or for detecting and measuring the properties and characteristics of underground substances, such as water, gases, contaminants, etc. Probes that test for underground substances are often used primarily in association with environmental applications. For instance, U.S. Pat. Nos. 6,208,940 and 6,236,941 both to Kram appear to describe a piezocone having a conical tip attached to the lower end of a smooth friction sleeve, where the sleeve measures the resistance of the soil. The Kram inventions use the piezocone to develop hydrostatic and hydraulic plots for detecting the depth of subsurface water and groundwater contamination.
In U.S. Pat. No. 5,663,649 to Topp, a soil penetrometer and method are disclosed which are capable of determining the soil moisture content via in situ measurements and simplified calculations. The penetrometer appears to have a releasably engageable tip and utilizes an electromagnetic field to detect moisture. Other prior art utilizes a variety of techniques in combination with penetrometers to detect and measure in situ characteristics, such as chemical composition for identification of contamination. For instance, U.S. Pat. No. 6,097,785 to Elam appears to disclose the use of a penetrometer equipped with x-ray fluorescence spectroscopy to identify hazardous waste; U.S. Pat. No. 6,147,754 to Theriault appears to use laser induced breakdown spectroscopy in conjunction with a penetrometer to identify soil contamination; U.S. Pat. No. 6,018,389 to Kyle appears to use fiber optic raman spectroscopy probes to provide in situ chemical analysis; and U.S. Pat. No. 5,497,091 to Bratton appears to teach the use of cone penetration testing (CPT) in conjunction with a surface-mounted pH sensor to provide continuous pH profiling with depth during penetration.
It is also known in subsurface testing systems to utilize cone and sleeve strain sensors to detect certain soil characteristics. In U.S. Pat. No. 5,635,710 to Reed, a detachable sleeve is apparently used to provide strength and protection to the radiation sensor probes which detect subsurface formations, and U.S. Pat. No. 5,902,939 to Ballard appears to disclose a penetrometer having cone and sleeve strain sensors used to calculate soil classifications and soil layers in “real-time” during penetration. Likewise, in U.S. Pat. No. 5,726,349 to Palmertree, a system and method for determining the shear resistance of soil with a portable and partially automated cone penetrometer is provided, where the field data outputs are stored and then transferred to a computer for tabulating.